I've had my 303 for about 4 years and had two problems.

1 Can't format my SM card.
It starts to format and then flashes the ERR. I've only tried it on the SM card that I've always had because they're nearly extinct and wonder if a new card would be better.

2 The filter/+drive
If I hit the filter/+drive I get bad static till I hit another button.

All tips welcome.

i dunno, i never had that problem but,...try a new card & see if you get the same message, the filter/drive button is unusual to me... the problem i had with mines was when i hit a pad the volume would cut low, eventually my the 303 stopped working, but i got it used...

I would try initializing the card according to the manual and see if that fixes your problem, if that doesn't work get a new card online and try to format it with the sp. If that doesn't do the trick, I would call Roland.

The 303 has a mind of its own. It says ERR any time it is in a bad mood. Blow some weed smoke on its effect knobs and you should be good.

I hear ya.. I havent used mine in a while but its not perfect.